Multicomponent kinetic determinations with the extended Kalman filter

Thesis (Ph. D.)--Michigan State University. Department of Chemistry, 1993Includes bibliographical reference

Paradoxically Decreased Signal Intensity on Postcontrast Short-TR MR Images

Seven lesions are presented in which short TRfshort TE images obtained immediately after IV administration of gadopentetate dimeglumine demonstrated an apparent decrease in signal intensity compared with precontrast short TRfshort TE images. All seven lesions were hyperintense on precontrast short TRfshort TE images. In four cases in which long TRflong TE scans were also obtained, the lesions were hypointense. This phenomenon may be due to a dominant T2 shortening effect by the contrast material that "overwhelms" T1 shortening even on short TRfshort TE scans. Other compounding factors may include variations in scanning variables, receive and transmit attenuations, or a photographic phenomenon due to window widths and center levels. The use of gadopentetate dimeglumine for evaluating CNS disease has become commonplace. With a standard dose of 0.1 mmolfkg , lesions that show contrast enhancement usually become bright on short TRfTE images. The explanation for this phenomenon is the shortening of T1 relaxation by the paramagnetic contrast agent on adjacent protons. As with any dipolar interaction , T2* shortening also occurs; however, its effect is usually inapparent on the short TR/short TE (T1-weighted) scans. We present seven cases in which there was a decrease in signal intensity after IV administration of contrast material in lesions that were hyperintense on precontrast short TR/short TE scans. Materials and Methods In the past 2 years we have observed seven cases in which there appeared to be a decrease in lesion signal intensity on postcontrast short TR (600-850)/short TE (20/30) images compared with precontrast scans. All scans were obtained on high-field 1.5-T scanners. Standard doses of gadopentetate dimeglumine (Magnevist, Berlex Industries , Wayne, NJ) at 0.1 mmolfkg were administered intravenously followed by immediate (i .e. ,< 5 min) postcontrast short TR scans. In three case

Variability in Surgical Treatment of Spondylolisthesis Among Spine Surgeons

Background There are a multitude of treatments for low-grade lumbar spondylolisthesis. There are no clear guidelines for the optimal approach. Objective To identify the surgical treatment patterns for spondylolisthesis among United States spine surgeons. Methods 445 spine surgeons in the United States completed a survey of clinical/radiographic case scenarios on patients with lumbar spondylolisthesis with neurogenic claudication with (S+BP) or without (S−BP) associated mechanical back pain. Treatment options included decompression, laminectomy with posterolateral fusion, posterior lumbar interbody fusion, or none of the above. The primary outcome measure was the probability of 2 randomly chosen surgeons disagreeing on the treatment method. Results There was 64% disagreement (36% agreement) among surgeons for treatment of spondylolisthesis with mechanical back pain (S+BP) and 71% disagreement (29% agreement) for spondylolisthesis without mechanical back pain (S−BP). For S+BP, disagreement was 52% for those practicing 5 to 10 years versus 70% among those practicing more than 20 years. Orthopedic surgeons had greater disagreement than did neurosurgeons (76% vs. 56%) for S+BP. Greater clinical equipoise was seen for S−BP than for S+BP regardless of surgeon characteristics. For spondylolisthesis without mechanical back pain, neurosurgeons were significantly more likely to select decompression-only than were orthopedic surgeons, who more commonly selected fusion. Conclusions Clinical equipoise exists for the treatment of spondylolisthesis. Differences are greater when the patient presents without associated back pain. Surgeon case volume, practice duration, and specialty training influence operative decisions for a given pathologic condition. Recognizing this practice variation will hopefully lead to better evidence and practice guidelines for the optimal and most cost-effective treatment paradigms

Application of Spatial Modulation of Magnetization to Cervical Spinal Stenosis for Evaluation of the Hydrodynamic Changes Occurring in Cerebrospinal Fluid

OBJECTIVE: To evaluate the hydrodynamic changes occurring in cerebrospinal fluid (CSF) flow in cervical spinal stenosis using the spatial modulation of magnetization (SPAMM) technique. MATERIALS AND METHODS: Using the SPAMM technique, 44 patients with cervical spinal stenosis and ten healthy volunteers were investigated. The degree of cervical spinal stenosis was rated as low-, intermediate-, or high-grade. Lowgrade stenosis was defined as involving no effacement of the subarachnoid space, intermediate-grade as involving effacement of this space, and high-grade as involving effacement of this space, together with compressive myelopathy. The patterns of SPAMM stripes and CSF velocity were evaluated and compared between each type of spinal stenosis and normal spine. RESULTS: Low-grade stenosis (n = 23) revealed displacement or discontinuity of stripes, while intermediate- (n = 10) and high-grade (n = 11) showed a continuous straight band at the stenotic segment. Among low-grade cases, 12 showed wave separation during the systolic phase. Peak systolic CSF velocity at C4-5 level in these cases was lower than in volunteers (p .05). In high-grade stenosis, both diastolic and systolic velocities were significantly lower (p <.05). CONCLUSION: Various hydrodynamic changes occurring in CSF flow in cervical spinal stenosis were demonstrated by the SPAMM technique, and this may be a useful method for evaluating CSF hydrodynamic change in cervical spinal stenosis.ope

Paracentesis: Faster and easier using the RenovaRP® pump

PURPOSEParacentesis is commonly performed in interventional radiology practice, and large volume paracentesis (LVP) using wall suction can take up to an hour to complete, placing significant stress on room and resource time. As the number of LVP procedures performed by Interventional Radiologists continue to increase, this study was undertaken to analyze the impact of the RenovaRP® Paracentesis Management System (GI Supply) on procedure time and patient satisfaction.METHODSBetween March 9, 2020 and May 29, 2020, procedural data and patient satisfaction was collected as part of a practice quality improvement project and retrospectively analyzed on 39 sequential paracenteses performed with wall suction prior to acquiring the RenovaRP® system and subsequently on 42 paracenteses performed with use of the device.RESULTSA substantially higher fluid flow rate was found using the RenovaRP® system compared to wall suction, 237.2 mL/min vs. 108.6 mL/min (P < .001). This resulted in a significant decrease in procedure room time from 53 min to 31 min (P < .001). There was associated improvement in the patient experience during paracentesis.CONCLUSIONThe RenovaRP® decreases procedure time for LVP with improvement in the patient experience during paracentesis

Suboccipital craniectomy with or without duraplasty: what is the best choice in patients with Chiari type 1 malformation?

The best surgical treatment for Chiari malformation is unclear, especially in patients with syringomyelia. We reviewed the records of 16 patients who underwent suboccipital craniectomy at our institution between 2005 and 2008. Of the six patients who did not undergo duraplasty, four showed improvement postoperatively. Two patients without syringomyelia showed improvement postoperatively. Of the four patients with syringomyelia, three showed improvement, including two with a decrease in the cavity size. One patient showed improvement in symptoms but the syringomyelia was unchanged. The cavity size increased in the one patient who did not show improvement. Among the 10 patients who underwent duraplasty, improvements were noted in four of the five patients without syringomyelia and in all of the five with syringomyelia. There is a suggestion that patients with syringomyelia may have a higher likelihood of improvement after undergoing duraplasty.A melhor opção de tratamento cirúrgico na malformação de Chiari é desconhecido, especialmente em paciente com siringomielia. Nós revisamos casos de 16 pacientes submetidos à craniectomia suboccipital em nossa instituição de 2005 à 2008. Dos 6 pacientes que não foram submetidos à duroplastia, quatro tiveram melhora pós operatória. Dois pacientes sem siringomielia tiveram melhora pós operatória. Dos quatro pacientes com siringomielia, três tiveram melhora, incluindo dois com diminuição do tamanho da cavidade. Um paciente teve melhora da sintomatologia mas a siringomielia não se modificou. Dez pacientes foram submetidos à duroplastia. Melhora foi observada em 4 de 5 pacientes sem siringomielia e 5 de 5 casos com siringomielia. Há uma sugestão de que pacientes com siringomielia possam ter uma maior taxa de melhora após serem submetidos à duroplastia

A comparative study on the efficacy of 10% hypertonic saline and equal volume of 20% mannitol in the treatment of experimentally induced cerebral edema in adult rats

<p>Abstract</p> <p>Background</p> <p>Hypertonic saline and mannitol are commonly used in the treatment of cerebral edema and elevated intracranial pressure (ICP) at present. In this connection, 10% hypertonic saline (HS) alleviates cerebral edema more effectively than the equal volume of 20% mannitol. However, the exact underlying mechanism for this remains obscure. This study aimed to explore the possible mechanism whereby 10% hypertonic saline can ameliorate cerebral edema more effectively than mannitol.</p> <p>Results</p> <p>Adult male Sprague-Dawley (SD) rats were subjected to permanent right-sided middle cerebral artery occlusion (MCAO) and treated with a continuous intravenous infusion of 10% HS, 20% mannitol or D-[1-³H(N)]-mannitol. Brain water content (BWC) as analyzed by wet-to-dry ratios in the ischemic hemisphere of SD rats decreased more significantly after 10% HS treatment compared with 20% mannitol. Concentration of serum Na⁺and plasma crystal osmotic pressure of the 10% HS group at 2, 6, 12 and 18 h following permanent MCAO increased significantly when compared with 20% mannitol treated group. Moreover, there was negative correlation between the BWC of the ipsilateral ischemic hemisphere and concentration of serum Na⁺, plasma crystal osmotic pressure and difference value of concentration of serum Na⁺and concentration of brain Na⁺in ipsilateral ischemic hemisphere in the 10% HS group at the various time points after MCAO. A remarkable finding was the progressive accumulation of mannitol in the ischemic brain tissue.</p> <p>Conclusions</p> <p>We conclude that 10% HS is more effective in alleviating cerebral edema than the equal volume of 20% mannitol. This is because 10% HS contributes to establish a higher osmotic gradient across BBB and, furthermore, the progressive accumulation of mannitol in the ischemic brain tissue counteracts its therapeutic efficacy on cerebral edema.</p